Throughout this application, various references are referred to within parentheses. Disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains. Full bibliographic citation for these references may be found at the end of this application, preceding the claims.
Multiple myeloma (MM) is an incurable B cell tumor affecting B cell end-stage differentiation. Clinically, the course of MM is similar to end-stage plasma cell leukemia (PCL), i.e., there is an uncontrollable proliferation of myeloma cells accompanied by numerous complications, including hyperviscosity syndromes, hypercalcemia, infections, multiple bone fractures, and organ failure.
Non-random chromosomal translocation is known to play a crucial role in the tumorigenesis of hematologic malignancies (1). In B-cell lymphomas, many important proto-oncogenes deregulated by juxtaposition to immunoglobulin (Ig) gene locus have been identified. Each proto-oncogene is associated with a specific subtype of lymphoma, such as c-MYC in Burkitt's lymphoma, Cyclin DI IBCLI in mantle cell lymphoma, BCL-2 in follicular lymphoma and BCL-6 in diffuse large cell lymphoma (2-8). In contrast, little is known about molecular alterations of human MM/PCL, due to the difficulty in cytogenetic analysis.
However, previous cytogenetic reports have shown a 14q+ chromosome, suggesting the existence of a chromosomal translocation involving the Ig heavy chain (IgH) locus, is observed in 20˜30% of the MM/PCL cases and it is the most frequent consistent abnormality (9-12). Even in such cases, most cytogenetic data have failed to identify donor chromosomes other than 11q13, 8q24, and 18q21, where proto-oncogenes Cyclin DIIBCL-IIPRADI, c-MYC and BCL-2 are located, respectively. Among them, the 11q13 locus has been demonstrated to be involved in nearly 5-10% of the cases and also in 62% of the established cell lines (13). The t(11;14) (q13;q32) translocation is also accompanied by a corresponding overexpression of the Cyclin D1 gene, which raises a strong possibility of the involvement of this gene, although the breakpoints at 11q13 do not cluster like those of the lymphoma cases (14-16). Recent advances in fluorescence in situ hybridization (FISH) have made it possible to clarify both the frequency of the 14q+ chromosomes and the partner chromosomes of the IgH loci. One such report revealed an intriguing result, i.e., that numerous chromosomal loci are able to translocate to IgH locus, including 6p21, 1q21, 3p11, 7q11, 11q23 (17). This has prompted a search for the proto-oncogenes deregulated by the regulatory elements of the IgH gene for a further understanding of the molecular mechanisms of MM/PCL. In the present study, one candidate proto-oncogene, MUM1 (multiple myeloma oncogene 1), was found juxtaposed to the IgH gene as a result of t(6;14)(p25; q32) translocation in human myeloma cell line, SKMM-1. Over expression of the MUM1 mRNA was observed in this cell line. A second gene, called MUM-2 was found translocated in proximity to the IgH gene on chromosome 14q32 in human myeloma cell line, U-266.
The method of analysis of 14q+ chromosomal translocations and identification of the genes altered in multiple myeloma of this invention are useful since 1) no method is currently available to determine the chromosomal sequences involved in 14q+ translocations, the most important cytogenetic lesions associated with MM pathogenesis; 2) no specific gene lesion is currently known for MM; 3) no diagnostic method based on gene/DNA lesion is currently available for MM and 4) there are no therapeutic approaches aimed at counteracting the action of abnormal gene products in MM.